Recombinant DNA technology has provided a new and abundant source of powerful genetic linkage markers in the form of restriction fragment length polymorphisms (RFLPs). The possibility of deriving a complete genetic linkage map of the human genome is now an achievable goal. We propose to use 3 large pedigrees from which many lymphoblastoid cell lines are already available as reference pedigrees for determining the linkage relationships of the new RFLP markers generated both by ourselves and by others. DNA from lymphoblast lines derived by transformation with Epstein-Barr virus will be prepared for all informative members of these pedigrees. It will then be digested with restriction enzymes, fractionated by agarose gel electrophoresis, transferred to a solid filter support, and probed with cloned human DNA fragments known to reveal polymorphisms. The genotype of an individual at a given locus will then be determined by examining the pattern of fragments detected by a hybridization probe from that locus. The linkage relationships of different RFLP markers will be examined using the LIPED computer program and, when appropriate, a Multi-point Mapping program. The genetic map which will be constructed using this data will have profound implications for all human genetic disease.